The trainee, who was not being used on NXT TV, had last been at the WWE Performance Center on June 9, when NXT TV tapings were happening.
The Wrestling Observer Newsletter reports that the wrestler who tested positive was a female wrestler in NXT, who has not been used on TV. She has been one of the fans used in the crowd, and was last used in that role on June 9th.
This COVID-19 positive test led to WWE nixing Tuesday's TV tapings and holding coronavirus testing instead.
It appears as if no one else has been infected by her, as there have been been no positive test results that have been reported.